Galling between the bushing and the track pin is a persistent problem in the track chains of tracked undercarriages. For example, U.S. Pat. No. 2,882,103 to Johnson et al. and patented in Apr. 14, 1959 attempted to solve this problem by including a chamfered portion inside each end of the bushing. While providing some benefit, galling problems between the pin and bushing have continued and been compounded by ever greater loads transmitted between the bushing and the track pin because of ever larger and more powerful machines. Specifically during use, the loads applied to the bushing and track pin cause the track pin to bend. The curvature of the track pin engages the edge of the chamfer such that edge loading can occur and result in galling and potentially premature failure. This edge loading between the track pin and the inner surface of the bushing is exacerbated by the greater loads transmitted through the interface between the track pin and bushing by ever larger, heavier equipment.
More recently, U.S. Pat. No. 6,846,051 to Bottom et al., patented on Jan. 25, 2005, attempted to solve this galling problem through the use of a free floating crown shaped insert. As stated in its abstract, “the crown shaped surface directs forces to the center of the insert to reduce edge loading.” While reducing edge loading, U.S. Pat. No. 6,846,051 has not solved the problem of edge loading which still occurs between the bushing and the track pin and continues to be a persistent problem in the track chains of tracked undercarriages, especially in the tracked undercarriages of ever larger machines.